In fibre based optical systems, signals propagate within optical fibers. When optically coupling two components, a fiber is coupled at a first end to a first component and at a second end to a second component. Often in an optical system, a plurality of fibers is routed within the system. When a large number of fibers are used, designs often incorporate ribbon fibers comprising a number of fibers and having a single connector at each end. The single multi-fibre connector is provided with bores or v-grooves for accepting optical fibers. Into each bore, a fiber is inserted and held in place.
Small irregularities or non-accuracies in ferrule and fiber manufacture can result in significant signal loss, particularly in coupling single mode fibers. A standard ferrule has an internal diameter closely matching a fiber diameter.
At times it is noted that different fibers within a cable have alignment errors; in this instance, it is nearly impossible to find two connectors that couple efficiently for all fibre pairs.
For more efficient installation of ribbon fibers, the coupling of multiple fiber ends at a single multi-fibre-connector pair, heretofore, has not been satisfactory. U.S. Pat. No. 5,671,311 to Stille et al. discloses a method of aligning a number of receiving ferrules within a less precise housing by providing aligning pins for locating the ferrule bores in the housing. Once the ferrules are positioned the fibers are then inserted. This is a rather imprecise method, which does not provide an opportunity to correct transmission problems once the fibers and light sources are in place. Also, since the fiber is inserted after the tuning is performed, slack between the ferule and the fiber can be a significant problem.
As of late, optical fibre sleeves have been manufactured with openings therein for accommodating optical fibers in two or more parallel rows. In this arrangement, the fibers are very closely spaced but preferably are not touching. The purpose of providing some space between adjacent optical fibers is to overcome the limitation of having adjacent fibers touch when the fibers' outer diameters vary from one another. Hence, providing accurately spaced holes within a sleeve offers an advantage.
In one instance, these sleeves are used as connector ends where the two or more parallel rows of one sleeve are used to couple with rows of optical fibers of a mating connector. Alternatively, a single-row or multi-row sleeve can be used as an optical fibre sleeve for coupling with another optical component such as an optical waveguide block, having waveguides disposed at an end thereof for coupling with the optical fibre ends within the single or multi-row sleeve. Within the specification the term sleeve shall not be confined to cylindrical sleeve and shall include other shapes such as a sleeve having a square or rectangular cross-section.
Within each row of the two parallel rows these sleeves or connector ends can be manufactured with substantially accurately spaced holes or grooves, however it is difficult to consistently align row holes and subsequently optical fibers within the two rows such that fibre 1 in row 1 is aligned with fibre 1 in row 2, fibre 2 in row 1 is aligned with fibre 2 in row 2, and so on. In other words, it is difficult to ensure that there is no lateral shift between the two rows of a same sleeve. It is also difficult to manufacture two parallel rows with a tight tolerance space, for example with .mu.m precision between the rows.
Currently, when an optical sleeve housing optical fibers in substantially parallel rows is found to have parallel rows of fibers wherein the rows are laterally offset more than a predetermined amount from one another, (about of 2 .mu.m) the sleeve is said to be outside acceptable tolerance for single mode optical fibre alignment and the sleeve is discarded.
An object of this invention is to provide a use for such sleeves that have parallel rows that are laterally offset and outside acceptable tolerances.
A further object of the invention is to provide a coupling device having a lens and a sleeve with parallel rows of optical waveguides that are laterally offset from one another.